"There are a lot of killers," Trump responded, before dropping his honesty bombshell.

"We've got a lot of killers. What do you think? Our country's so innocent?"

Michael McFaul, a former ambassador to Russia and advisor to former president Barack Obama, described Trump's comments as "disgusting."

"This moral equivalency that Trumps continues to draw between the USA and Russia is disgusting (and inaccurate)," he said on Twitter.

Mainstream Republicans have repeatedly called on Trump to distance himself from Putin, with little impact.

Throughout the election campaign, Trump refused to criticize the Russian leader, saying better relations with the Kremlin would be in the US national interest.

The new president has advocated working with Russia to combat the Islamic State group in Syria, where Moscow has deployed aircraft, naval assets and troops to support Bashar al-Assad's regime.

In December, US intelligence agencies went public with their view that Russia conducted a hack-and-release campaign aimed at swinging the US election in Trump's favour.

Trump's repeated criticism of NATO -- a common target for Putin -- has only fuelled suspicions that Trump is ready to side with Moscow over allies in Europe.

Across Europe, there are growing concerns that the continent might be wedged between a hostile Russia and a hostile United States.

Trump's stance on Ukraine has also raised eyebrows. After a call with Ukrainian leader Petro Poroshenko on Sunday, the White House said the pair addressed "Ukraine's long-running conflict with Russia."

Russia annexed the Ukrainian region of Crimea in March 2014 and has supported separatists in the east of the country.

Former national security advisor Susan Rice publicly criticized Trump's framing of the situation.

"This distortion of even recent history is deeply troubling," she tweeted.